WO2012113221A1

WO2012113221A1 - Equalization method and system for discharge of power lithium ion battery pack

Info

Publication number: WO2012113221A1
Application number: PCT/CN2011/079357
Authority: WO
Inventors: 王明旺; 李武歧; 李载波
Original assignee: 欣旺达电子股份有限公司
Priority date: 2011-02-23
Filing date: 2011-09-05
Publication date: 2012-08-30
Also published as: CN102651560A

Abstract

Disclosed are an equalization method and system for discharge of a power lithium ion battery pack, which relate to the technical field of power battery management. The present invention provides a method and a system for implementing equalization when a battery pack is almost discharged to empty. In the present invention, when the discharge is about to end, that is, remaining charge quantity of the battery pack is 20% to 30%, a discharge equalization measure is started: properly reducing output voltages at positive and negative poles of the battery pack, and loading the voltages to positive and negative poles of a small part of single batteries having low voltages for compensating charge, so as to reduce the speed of discharging the low-voltage battery to empty, such that all the single batteries reach an empty state almost at the same time, thereby prolonging the discharge time. The present invention equalizes differences among single batteries, prolongs the service life of the battery pack, and has low power consumption, higher efficiency, and better effects.

Description

TECHNICAL FIELD The present invention relates to the field of power battery management technologies, and in particular to an automotive lithium ion battery discharge equalization method and an equalization system. BACKGROUND OF THE INVENTION In order to meet the requirements of voltage, power and energy during operation of high-power equipment such as electric vehicles, battery packs are often composed of a large number of power batteries connected in series. Although the difference between the batteries is gradually reduced as the technical process is improved, it is still difficult to ensure that the characteristics of each battery are completely uniform at the current manufacturing level. Especially under the operating conditions of the operating conditions, irregular charging and discharging are frequently performed, and the difference between the batteries deteriorates after the battery pack is operated for a while, so that the use efficiency of the battery pack is lowered and the life is reduced.

Inconsistencies between cells cannot be completely eliminated, especially since this inconsistency has existed at the beginning of its production. In order to protect the life of the battery pack, a battery management system has emerged. Its main job is to find the difference between the batteries and shrink, which is commonly referred to as battery balancing technology.

Generally, the equalization state is: the absolute difference between the average voltage of each single cell and the voltage of each single cell is less than a set threshold, and the set threshold may be 0.1 according to the accuracy requirement of the equalization system. V, may also be a set value for other people, such as 0.08V, 0.12V, and so on. At present, the main method for solving the inconsistency in the discharge process is to discharge the relatively high voltage single cell through the shunt resistor. This equalization method is to lower the voltage of the relatively high voltage cell and accelerate the high voltage battery. The discharge speed is such that all of the single cells reach the venting state almost simultaneously. In this way, not only the power consumption is generated, but actually the discharge time of the battery pack is shortened because the discharge time of the equalization method is determined by the single cell having the lowest capacity. Moreover, the discharge resistance is fixed in size, and the discharge current is not adjustable, which may cause partial discharge or partial over-discharge, which eventually leads to poorer battery balance.

Correction page (Article 91) SUMMARY OF THE INVENTION A first object of the present invention is to provide: a power lithium ion battery pack discharge equalization method with longer discharge time and better balance effect.

A second object of the present invention is to provide: A power lithium ion battery discharge equalization system, which is advantageous for making the power lithium ion battery pack have a longer discharge time, and the equalization effect in the discharge process is better balanced and balanced.

According to an embodiment of the present invention, a power lithium ion battery pack discharge equalization method includes: the lithium ion battery pack includes a plurality of single cells connected in series, and the positive and negative ends of each of the single cells respectively pass through a switch circuit Cooperating electrically with the output end of the DC conversion circuit that is always flowing to the DC, the input end of the DC conversion circuit is electrically connected to the voltage output end of the lithium ion battery; during the discharge of the 4 ion battery pack And monitoring the residual charge amount of the lithium ion battery pack in real time. When the ratio of the remaining charge amount of the lithium ion battery pack to the total capacity of the lithium ion battery pack reaches a predetermined lower limit, the following steps are sequentially performed:

Collecting a voltage signal of each of the single cells to obtain a voltage measurement value of each of the single cells; determining a current battery that needs to be compensated for charging according to a voltage measurement value of each single cell; a switching circuit electrically connected to the charged unit battery, wherein the output end of the DC conversion circuit is in electrical communication with the positive and negative poles of the unit battery currently required to be compensated for charging, so that the DC conversion circuit is currently required to compensate for charging The single cell compensates for charging until the end of the discharge of the lithium ion battery.

Optionally, the predetermined lower limit is selected from any value between 20% and 30%. Optionally, according to the voltage measurement value of each single battery, the single battery that needs to be compensated for charging is determined according to a predetermined program, specifically:

Correction page (Article 91) Calculating and determining the average value of the current voltage measurement value according to the voltage measurement values of all the single cells,

Comparing and calculating the absolute difference between the voltage measurement value of each single cell and the average value of the voltage measurement value, and using the single cell whose absolute difference is greater than a predetermined threshold as a candidate cell to be equalized, from high to Lowly sorting the voltage measurement values of the candidate cells to be equalized to obtain a sorting queue, and sorting the voltage measurement values by a predetermined number of single cells at the end of the sorting queue as the single cells that need to be compensated for charging. Optionally, the predetermined number is: an integer value of 10% of the total number of single cells. A power lithium-ion battery pack discharge equalization system provided by an embodiment of the present invention includes: the power lithium-ion battery pack includes a plurality of single cells connected in series, and the equalization system includes: a plurality of lower-level machines and a plurality of switch circuits , a host computer and a DC to DC DC conversion circuit;

The output ends of the circuit are electrically connected in common, and the input end of the DC conversion circuit is electrically connected to the voltage output end of the lithium ion battery pack;

Each of the lower-level machines is electrically connected to the positive and negative poles of each of the single cells, respectively, for collecting voltage signals of the single-cell batteries, obtaining voltage measurement values of the single-cell batteries, and each single-cell battery The voltage measurement value is transmitted to the upper computer; the upper computer includes: a battery remaining power detection module, a compensation rechargeable battery determination module, and a compensation charging control module, wherein the compensation charging battery determination module and each of the lower positions An electromechanical connection, configured to determine, according to a predetermined voltage program, a single battery that is currently required to be compensated for charging according to a predetermined procedure, wherein the remaining battery power detecting module is electrically connected to the bus bar of the lithium ion battery pack, Yu

Correction page (Article 91) Determining a residual charge amount of the lithium ion battery pack according to a bus voltage and a bus current, wherein the compensation charging control module and the battery group remaining power detecting module, the compensation charging battery determining module, each lower position machine, and each switching circuit are respectively powered Connecting, when the ratio of the remaining charge amount of the lithium ion battery pack to the total capacity of the ion battery pack is less than or equal to a preset lower limit. · starting each of the lower position machine, compensating the rechargeable battery determination module, and connecting The switch circuit for electrically connecting the charged battery cells is currently required to electrically connect the output end of the DC conversion circuit to the positive and negative terminals of the battery unit currently required to be compensated for charging, so that the DC conversion circuit is current The rechargeable battery is compensated for charging until the lithium ion battery pack is discharged. Optionally, the predetermined lower limit is selected from any value between 20% and 30%. Optionally, the compensation charging battery determination module includes: a threshold comparison module, which is electrically connected to each of the lower computers, and is used for comparing and calculating the average value of the voltage measurement value of each single battery and the voltage measurement value. An absolute difference; a sorting sub-module, respectively connected to the threshold comparison module and each lower electromechanical, for sorting the voltage values of the candidate cells to be equalized from high to low, to obtain a sorting queue, wherein the candidate to be equalized The battery is: a single cell determined by the threshold comparison module and having an absolute difference greater than a predetermined threshold; a compensated rechargeable battery determination sub-module electrically connected to the sequencing sub-module for scheduling the end of the sorting queue The number of single cells, as the battery cells currently required to compensate for charging, optionally, the predetermined number is: an integer value of 10% of the total number of cells. The upper computer is also electrically connected to a temperature sensor. Optionally, a display module is further electrically connected to the upper computer. Optionally, each of the lower computers is a programmable logic controller or a single chip microcomputer. Optionally, each of the switching circuits is a field effect transistor.

Correction page (Article 91) It can be seen from the above that the technical solution of the embodiment of the present invention is applied, so that all the single cells in the power lithium ion battery pack are emptied together, thereby ensuring the balance performance of the overall power lithium ion battery pack and ensuring long-term discharge power supply. The measure taken in the embodiment of the present invention is to start the discharge equalization measure at the end of the discharge: DC output change of the output voltage signal of the power lithium ion battery pack (ie, the bus voltage signal of the power lithium ion battery pack) The voltage is converted, so that the DC conversion circuit passes through the switch switching circuit, and is input to the single battery that needs to be compensated for charging.

(the current single cell with a lower cell voltage), thereby charging it to reduce the speed of the charge of these cells, so that all the cells in the lithium-ion battery can reach the venting almost simultaneously. The state, which in turn extends the discharge time. Moreover, in the equalization measure of the present invention, the voltage source for providing compensation charging for the unit battery that needs to be compensated for charging is a power lithium ion battery pack (a collection of all the single cells), so the compensation charging in the embodiment of the present invention is actually one. The self-transfer of energy in the power battery pack is less energy-consuming than the prior art using an additional DC power source for compensating charging. The lithium ion battery pack discharge equalization system of the present invention, through a plurality of lower position machines, each lower position machine separately collects voltage signals of the respective single cells to obtain voltage measurement values of the respective single cells, and in this embodiment, each The invention has more precise and flexible discharge balance control for lithium ion battery packs and higher efficiency. In addition, in this embodiment, since the entire lithium ion battery pack discharge equalization system adopts a bottom-up modular structure, for example, each lower position machine is responsible for voltage collection of each single battery, and the upper computer is responsible for the actual remaining capacity of the entire power battery. Detection and overall centralized management, the top-down layered modular setup makes lithium-ion battery pack discharge equalization system more convenient to maintain, system upgrade and compatibility. In summary, the technical solution of the embodiment of the present invention has lower energy consumption than the existing battery-discharge equalization method and device of the automobile battery pack, and the difference between the individual cells of the street and the battery life of the battery pack are extended. More efficient and better.

Correction page (Article 91) BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are set forth in the drawing of FIG

1 is a schematic flow chart of a power lithium-ion battery pack discharge equalization method in a discharge process according to Embodiment 1 of the present invention;

2 is a schematic diagram showing the principle of a connection circuit of a power lithium ion battery pack, a switch circuit, and a DC conversion circuit according to Embodiments 1 and 2 of the present invention;

3 is a schematic structural diagram of a power lithium-ion battery pack street-street system provided in Embodiment 2 of the present invention;

4 is a schematic diagram showing the structure principle of a power lithium ion battery equalization system according to Embodiment 3 of the present invention. The present invention will be described in detail with reference to the accompanying drawings and specific embodiments.

Example 1:

This embodiment discloses a power lithium ion battery pack discharge equalization method. The lithium ion battery pack includes a plurality of single cells connected in series, and the single cells are connected in series to provide a higher voltage for external power supply. The ion battery pack can be, but is not limited to, applied to automobiles and the like. The power lithium ion battery pack discharge equalization method of the embodiment is mainly applied to the difference between the individual cells when the balanced lithium ion battery pack is in a discharge state, so that the charge amount of each single cell in the discharge process is kept high. Consistency, in order to achieve the venting state of each cell in the lithium-ion battery pack.

The application of the power lithium-ion battery pack discharge equalization method of the embodiment is mainly as follows:

Correction page (Article 91) under:

The positive and negative ends of each single cell are respectively connected to a direct current through a switching circuit.

The output terminals of the DC-DC (DC-DC) are electrically connected together, that is, each switch circuit is connected between each unit cell and the output terminal of the DC conversion circuit, and the single battery can be controlled by controlling the on/off of the switch circuit. The on/off of the DC conversion circuit. The input end of the DC conversion circuit is electrically connected to the voltage output end of the lithium ion battery, that is, the DC conversion circuit of the embodiment mainly passes the output DC signal of the lithium ion battery through DC-DC conversion, and the output is suitable for the pair. The DC voltage signal charged by the single battery.

Referring to FIG. 1, during the discharge process of the lithium ion battery, the discharge equalization method of the embodiment mainly includes the following steps: Step 101: Monitor the residual charge amount of the lithium ion battery in real time. During the discharge of the lithium ion battery pack, the remaining charge amount of the lithium ion battery pack is periodically monitored at a predetermined frequency.

The determination of the amount of remaining charge of the lithium ion battery pack can be, but is not limited to, by measuring the bus voltage of the lithium ion battery and the bus current, and then determining the lithium ion by the current bus voltage U(t) and the bus current I(0, calculated. The current remaining charge of the battery pack: Q ( t ) = U ( t ) * I ( t ).

Step 102: Determine whether the ratio of the remaining charge amount of the lithium ion battery pack to the total capacity of the local ion battery pack reaches a predetermined lower limit. If yes, go to step 103; otherwise, return to step 101. The amount of residual charge in the embodiment of the invention may be, but is not limited to, characterized by the ratio of the amount of remaining charge relative to the nominal capacitance of the power lithium ion battery.

After determining the current residual charge amount of the lithium ion battery pack, determining whether the current residual charge amount of the lithium ion battery pack accounts for a predetermined lower limit of the total capacity of the lithium ion battery pack, and if yes, executing step 103, Start the compensation charging strategy. Otherwise, return to step 101 to continue the remaining battery monitoring of the lithium-ion battery pack.

Correction page (Article 91) In this embodiment, when the current residual charge amount of the lithium ion battery pack reaches 30% of the capacity of the lithium ion battery pack, it is determined that the initial compensation charging strategy needs to be performed, and step 103 is performed. It should be noted that, after a plurality of experimental studies by the inventors, it is determined that the predetermined lower limit value in the embodiment may also be selected from any of 20% to 30%, and the specificity may be determined according to actual experience. Lower limit value. Step 103: Collect voltage signals of the individual cells to obtain voltage measurements of the cells. The voltage signal of each of the single cells is detected on each of the unit cells by a voltage measuring module or a device with the voltage measuring module, and current voltage measurements of the respective cells are obtained. In the specific implementation, modules such as a single-chip microcomputer or a Programmable Logic Controller (PLC) are respectively connected to the positive and negative terminals of each single cell, and the positive and negative electrodes of each single cell are collected in real time. The voltage signals at both ends, and then the currently collected analog voltage signals are converted into computer-recognizable digital signals by signal processing such as amplification, digital-to-analog conversion, etc., to obtain voltage measurement values of the individual cells. Step 104: According to the voltage measurement value of each single battery, determine the current battery that needs to be compensated for charging. Because the current voltage measurement value of the single battery reflects the current residual charge of the single battery, in this step, each monomer The voltage measurement of the battery determines that the current voltage measurement value is lower (ie, the current residual charge amount of the single cell) is determined as: The current battery that needs to be compensated for charging. In this embodiment, the equalization method of the lithium ion battery pack according to the prior art may be used to determine which single cells should be equalized, for example, the voltage measurement values of all the single cells, and the calculation determines the current The average value of the voltage measurement values is then compared and calculated to obtain an absolute difference between the voltage measurement value of each unit cell and the average value of the voltage measurement value, and the single cell in which the absolute difference value is greater than a predetermined threshold value is taken as the current A battery that needs to be balanced (requires compensation for charging). However, the inventors found in the study of the present invention that the technical solution of the embodiment of the present invention

Correction page (Article 91) In the above, the result obtained by the above threshold comparison scheme may be that the current large number of single cells are batteries that need to be balanced. If the number of cells to be balanced is large, the energy required for self-equalization in the lithium-ion battery pack is large, so that the output power of the entire lithium-ion battery pack is reduced, which is not conducive to actual promotion. To this end, the inventors have developed the following method for determining the current cell to be compensated for charging, specifically: First, based on the voltage measurement values of all the cells, the average value of the current voltage measurement is determined. . For example: Currently there are 100 single cells, the current voltage measurement values of the single cells D0, D2 D99 are V0, VI, V2... V99, respectively, then calculate the average value:

V _Ave =SUM(V0:V99)/100. Then, the absolute difference between the voltage measurement values (V0, VI, V2, ..., V99) and the average value V _Ave of each of the single cells is separately calculated, and the single cell whose absolute difference is greater than a predetermined threshold is used as Candidate cells to be equalized. The size of the threshold may be determined according to actual conditions, such as but not limited to being determined to be 0.1V, "may also be a value set by other people, such as 0.08V, 0.12V, etc. The present inventors will The threshold is set to 0.2 V. Then, the voltage measurement values of the candidate cell to be equalized are sorted from high to low to obtain a sorting queue. In the sorting queue, the voltage measurement values at the head of the queue are compared. High, the voltage measurement at the end of the sorting queue is lower, and the voltage measurement at the end of the sorting queue is lower. Finally, the voltage measurements are sorted at a predetermined number of N cells at the end of the sorting queue, as At present, it is necessary to compensate for the charging of the single battery. The part of the single battery that has the lowest current voltage at the end of the sorting queue (ie, the current remaining amount of charge is the lowest) is used as the unit battery that needs to be compensated for charging. The N value can be, but not It is limited to the integer value of the 10% pool of the total number of cells. For example, when the number of cells in the current lithium-ion battery pack is 100, the total cell power is The 10% of the pool number has an integer value of 100*10%=10. That is, the last 10 voltage measurements in the sorting queue are selected.

Correction page (Article 91) The single cell corresponding to the trial value is used as the single cell that needs to be compensated for charging. After the threshold comparison is performed, the result of the threshold comparison is further determined: the voltage measurement values of the candidate cell to be equalized are sorted from high to low, and only a predetermined number of monomers having the lowest voltage measurement value are selected. The battery acts as a single battery that actually needs to be compensated for charging. By adopting the technical scheme of the embodiment, on the one hand, it is ensured that the output power of the lithium ion battery pack can be used to charge the single battery in the lithium ion battery pack during the discharge process of the lithium ion battery pack to avoid partial lithium ion battery. Premature venting results in a shorter discharge time of the overall lithium-ion battery pack; avoiding the use of excessive energy for compensating charging of the battery cells in the battery pack, resulting in insufficient output power of the entire lithium-ion battery pack, so this implementation The technical solution provided by the example to determine the current battery cell to be compensated for charging is more suitable for practical implementation.

Step 105: Turn on a switch circuit electrically connected with the unit battery that needs to be compensated for charging, so that the output end of the DC conversion circuit is in electrical communication with the positive and negative poles of the unit battery that needs to be compensated for charging.

After the unit cells that need to be compensated for charging are determined in step 104, in this step, the compensation charging is started for the cells that are currently required to be compensated for charging, specifically:

Switching a switching circuit electrically connected to a battery cell currently required to compensate for charging, so that the switching circuits are in an on state, that is, an output end of the DC conversion circuit on one side of the switching circuit and a single cell on the other side of the switching circuit The positive and negative poles are in electrical communication.

For example, in the power battery pack shown in FIG. 2, it is determined in step 104 that the single cells that need to be compensated for charging are D9, D8 D1, and DO, respectively connected to the single cells D9, D8 Dl,

The switching circuits between the DO and the DC conversion circuit are K 9 , Κ 8 ... K l, Κ 0, respectively.

In this embodiment, the switch circuit Κ 9, Κ8 Κ 1, Κ 0 is specifically turned on, so that the switch circuit Κ

9. Κ8... Κ 1, Κ 0 is in the on state. At this time, the DC conversion circuit converts the output signal of the lithium-ion battery pack at the input end to DC signal after DC-DC conversion. Switch

Correction page (Article 91) The circuit K9, Κ8 K l, Κ 0 is input to the single cells D9, D8 D1, DO, and the battery cells D9, D8 D1, DO are compensated and charged until the discharge of the entire lithium ion battery pack is completed. Because the discharge time of the lithium-ion battery pack is based on the short-board effect principle of the wooden barrel (how much water a bucket can hold, it does not depend on the longest piece of wood, but on the shortest piece of wood): that is, the entire power The length of discharge of the battery pack depends on the cell battery that is emptied at the earliest. As long as one of the cells of the entire lithium ion battery pack is emptied, the entire lithium ion battery pack stops discharging. In the embodiment, the current voltage measurement value is lower when the entire lithium ion battery pack is quickly emptied (that is, when the current remaining capacity of the entire lithium ion battery pack reaches a predetermined lower limit) (ie, the current order) The battery cells with low residual charge of the body battery are compensated for charging to slow down the discharge of the charge of the cells, so that all the cells in the lithium-ion battery can reach the venting almost simultaneously. State, which in turn extends the discharge time. In the prior art, a technical solution of applying a DC power supply to supplement the power is mainly used. Since the external power source generates heat when the current is supplied, and the supplied DC power source flows through the fixed resistor, the resistor consumes part of the energy, and since the resistance is fixed, The charging current of the supplementary charging is not adjustable, so the battery cannot be accurately discharged. In the case of compensating charging, sometimes the compensation may be too large and sometimes the compensation may be too small, which further exacerbates the uniformity of the lithium ion battery pack, and the existing The complexity of the compensation charging circuit in the technology is not easy to implement.

In this embodiment, the DC conversion circuit can reduce the voltage across the positive and negative terminals of the lithium ion battery pack to a charging voltage that can be used to charge the current battery that needs to be compensated for charging, and the current charging to be compensated. The body battery is charged to realize energy transfer, and when realized, the DC conversion circuit is electrically connected to each unit battery through a controllable switching circuit, so that accurate compensation charging of a single battery can be realized. In the charging and charging process of a single battery, the other single cells are disconnected due to the electrically connected switching circuit, that is, they are isolated from the DC circuit, and the working state is not affected.

It should be noted that, in the embodiment of the present invention, the equalization measure is started when the residual charge of the battery pack is only 20% to 30%, instead of starting the equalization measure at the beginning of the discharge, specifically, the inventor corrects the page (Details) 91) During the long-term test of the present invention, it was found that the energy transfer equalization measures adopted by the present invention objectively have a certain degree of consumption in the energy transfer process. If the equalization measure is initiated at the beginning, the battery pack will continue to consume its own energy, which in turn will reduce the discharge time of the battery pack. Moreover, the purpose of equalization is to enable all single cells to be fully charged and fully discharged at the same time. Then, equalization measures are taken in the later stage of discharge, which not only can achieve the purpose of equalization, but also can consume less energy for self-equalization, thereby extending Discharge time. In summary, according to the technical solution of the embodiments of the present invention, in order to achieve the venting of all the single cells in the power lithium ion battery pack, thereby ensuring the balanced performance of the overall power lithium ion battery pack and ensuring long-term discharge power supply, The measure taken in the embodiment of the present invention is to start the discharge equalization measure at the end of the discharge: DC-transformed the output voltage signal of the power lithium-ion battery pack (ie, the bus voltage signal of the power lithium-ion battery pack) through the DC conversion circuit The conversion is converted by the DC conversion circuit through the switch switching circuit to the single cell (currently the cell with a lower cell voltage) that is currently required to be compensated for charging, thereby charging the battery to reduce the charge of the cells. The speed of venting, so that all the cells in the lithium-ion battery pack can reach the venting state almost simultaneously, thereby prolonging the discharge time. Moreover, in the equalization measure of the present invention, the voltage source for providing compensation charging for the unit battery that needs to be compensated for charging is a power lithium ion battery pack (a collection of all the single cells), so the compensation charging in the embodiment of the present invention is actually one. The self-transfer of energy in the power battery pack is less energy-consuming than the prior art using the additional DC power source for the compensation of the charging power. Example 2:

As shown in FIG. 2, this embodiment discloses a discharge equalization system for a power lithium ion battery pack. The lithium ion battery pack includes a plurality of single cells (D0, D1 ... DN) connected in series, and the single cells (D0, D1 ... DN) are connected in series to provide a higher The voltage is externally supplied, and the power lithium ion battery pack can be, but is not limited to, applied to automobiles and the like. The power lithium ion battery pack discharge equalization system of the embodiment is mainly applied to the difference between the single cells (D0, D1, ... DN) when the balanced power lithium ion battery pack is in a discharge state, thereby

Correction page (Article 91) During the electric process, the charge of each unit cell (D0, Dl ... DN) is kept high, so as to achieve the individual cells in the lithium ion battery pack (D0, Dl .... .. DN) At the same time, the venting state is reached. The power lithium ion battery pack discharge equalization system provided by the embodiment mainly includes: a plurality of lower position machines (J0, J1 ... JN), a plurality of switch circuits (K0, 1... ΚΝ), a host computer 300 and a DC to DC DC converter circuit S0. Among them, the number of lower computers (J0, J1... JN), and the switching circuits (K0, K1... ΚΝ) and the single cells (D0, Dl ... DN) The number is the same. The connection relationship of each component is mainly as follows: Each lower position machine (J0, J1, ... JN) is electrically connected to the positive and negative poles of each of the single cells (D0, D1, ... DN), respectively. Collecting voltage signals of each of the single cells (D0, D1, ... DN), obtaining voltage measurement values of each of the single cells (DO, D1, ... DN), and each of the individual cells The voltage measurement values of ( DO, Dl ... DN) are transmitted to the upper computer 300, and each lower computer (J0, J1 ... JN) pairs the single cells (D0, D1..... DN) The acquisition of the voltage signal can be, but is not limited to, shown in step 103 in Embodiment 1, and is not described herein. Each lower computer (J0, J1... JN) is a PLC or a single chip microcomputer. Each of the switching circuits (K0, K1, ...) is electrically connected to the positive and negative terminals of each of the single cells (D0, D1, ... DN) and the output of the DC conversion circuit SO. The input end of the DC conversion circuit SO is electrically connected to the voltage output terminal of the lithium ion battery pack. Each of the switching circuits (K0, K1, ...) can be a field effect transistor. In the specific implementation, each of the lower computers (J0, J1, ... JN) can be set in each single battery (D0,

Dl ...... DN), avoiding the measurement error caused by long-line traces, resulting in insufficient balance accuracy, so that the measured voltage parameters of each single cell (D0, Dl ... DN) are more accurate. High, so the accuracy of the subsequent equalization scheme based on these voltage parameters is correspondingly higher, which is more in line with actual needs. The upper computer 300 is mainly used as a centralized control unit of the entire lithium ion battery pack, and is mainly used for monitoring the actual remaining capacity of the power lithium ion battery pack, and is reported according to each lower position machine (J0, J1, ... JN). The voltage measurement value of each single-cell lithium-ion battery is determined by the program to determine the low-voltage single-cell battery (D0, Dl ... DN) that needs to be compensated for charging, and the compensation charging strategy starts to charge the current compensation. The low-voltage single cells (D0, Dl... DN) are replenished in time to achieve battery balancing

Correction page (Article 91) of. The upper computer 300 is a main control module including a CPU.

The upper computer 300 mainly includes: a battery remaining power detecting module 301, a compensated rechargeable battery determining module 302, and a compensation charging control module 303. The connection relationship and working principle of each module are as follows:

The compensated rechargeable battery determination module 302 is electrically connected to each of the lower position machines (J0, J1, ..., JN) for measuring the voltage values of the respective battery cells (D0, D1, ... DN). The predetermined procedure determines the cells (D0, D1... DN) that are currently required to compensate for charging. The working principle of the compensated rechargeable battery determination module 302 can be, but is not limited to, described in step 104 of the embodiment, and details are not described herein. The battery remaining power detecting module 301 is electrically connected to the bus bar of the lithium ion battery pack for determining the remaining charge amount of the lithium ion battery pack according to the bus voltage and the bus current. The working principle of the battery-remaining power detecting module 301 can be, but is not limited to, shown in step 101 in Embodiment 1, and details are not described herein. The compensation charging control module 303 and the battery remaining power detecting module 301, the compensated rechargeable battery determining module 302, the lower computers (J0, J1, ... JN), and the respective switching circuits (K0, K1, ...) ΚΝ) respectively, electrically connected, when the ratio of the remaining charge of the lithium ion battery to the total capacity of the lithium ion battery is less than or equal to a preset lower limit (the lower limit of the preset may be, but is not limited to, selected from 20% to 30) When any value between %), each lower computer (J0, J1 ... JN) is activated, the rechargeable battery determination module 302 is compensated, and the single battery (D0, D1.. .... DN) electrically connected switching circuit (K0,

K1... ΚΝ), the output end of the DC conversion circuit SO and the current battery that needs to be compensated for charging

The positive and negative poles of (D0, D1, ... DN) are electrically connected, so that the DC conversion circuit SO compensates and charges the single cells (D0, D1, ... DN) that are currently required to be compensated for charging. Until the lithium ion battery pack is discharged. The working principle of the compensation charging control module 303 can be specifically, but not limited to, the description in the steps 102 and 105 in the embodiment 1, and details are not described herein. Since the discharge time of a lithium-ion battery pack is based on the short-board effect principle of a wooden barrel (how much water a bucket can hold, it does not depend on the longest piece of wood, but on the shortest piece of wood): that is, the whole

Correction page (Article 91) The length of the discharge time of the power battery pack depends on the single cell (DO, D1...DN) that is emptied at the earliest, as long as a single cell of the entire lithium-ion battery pack (D0, D1... When DN) is vented, the entire lithium-ion battery pack stops discharging. It can be seen from the above that, with the technical solution of the embodiment, the entire lithium-ion battery pack discharge equalization system adopts a modular structure from bottom to top, and each lower position machine (J0, J1 ... JN) is responsible for each single battery. (D0,

D1... DN) voltage acquisition, the upper computer 300 is responsible for the actual remaining capacity detection of the entire power battery and the overall centralized control management. The top-down hierarchical modular setting enables the lithium ion battery pack discharge equalization system maintenance. More convenient, system upgrades and compatibility are better, control is more precise and flexible, and more efficient.

The above-mentioned lithium ion battery pack discharge equalization system is adopted, and the lower position machine (J0, J1 ... JN), the upper computer 300, the switch circuit (K0, K1 ... KN), and the DC conversion circuit are used. With the cooperation of SO, the discharge equalization measure can be started at the end of discharge: DC output voltage signal (ie, the bus voltage signal of the power lithium-ion battery pack) of the power lithium-ion battery pack is DC-converted by the DC conversion circuit SO, Therefore, the DC conversion circuit SO passes through the switch switching circuit, and is input to the single battery (the single cell with a lower cell voltage) of the current charging device, thereby charging compensation thereof to slow down the charge of the single cells. The speed of the venting is such that all of the cells (D0, D1, ... DN) in the lithium-ion battery pack can reach the venting state almost simultaneously, thereby prolonging the discharge time. Moreover, in the equalization measure of the present invention, the voltage source for providing compensation charging for the unit cell currently requiring compensation charging is a power lithium ion battery pack (a collection of all the single cells D0, D1 ... DN), The compensation charging in the embodiment of the present invention is actually a self-transfer of energy in the power battery pack. Compared with the prior art, an additional DC power supply is used to compensate the charging, and the energy consumption in the technical solution is less. Embodiment 3: Referring to FIG. 4, the power lithium ion battery discharge equalization system provided in this embodiment is different from the system shown in FIG. 3 in that:

Correction page (Article 91) The compensated rechargeable battery determination module 302 of the present embodiment includes: a threshold comparison module 405, a sequencing sub-module 401, and a compensated rechargeable battery determination sub-module 402. The threshold comparison module 405 is electrically connected to each of the lower computers (J0, J1, ..., JN) for comparing and calculating the voltage measurement of each of the single cells (D0, D1, ... DN). The absolute difference between the value and the average value of the voltage measurement value; the sorting sub-module 401 is electrically connected to the threshold comparison module and each of the lower-level machines (J0, J1, ..., JN) for sorting from high to low by high To sort the voltage values of the candidate cells to be equalized to obtain a sorting queue; wherein, the candidate cells to be equalized are: a single cell determined in the threshold comparison module and having an absolute difference greater than a predetermined threshold.

The compensated rechargeable battery determination sub-module 402 is electrically coupled to the sequencing sub-module 401 for using a predetermined number N of cells at the end of the sorting queue as the single battery that is currently required to be compensated for charging.

The single-cell battery of 10% of the total number of cells of the end of the sorting queue as described in Embodiment 1 may be taken as the cell to be compensated for charging. For example, if the total number of single cells in the current battery group is 100, then the 10 cells corresponding to the voltage measurement value are used as the single cells that need to be compensated for charging.

Specifically, but not limited to, the corresponding description in step 104 of Embodiment 1 is referred to. For example, in the power battery pack shown in FIG. 2, it is determined in step 104 that the single cells that need to be compensated for charging are D9, D8 D1, and DO, respectively connected to the single cells D9, D8 Dl,

9, 8... Κ 1, Κ 0 is in the on state, at this time, the DC conversion circuit converts the output signal of the lithium-ion battery pack at the input end to DC signal after DC-DC conversion. The switching circuit K 9 , Κ 8 ... Κ Κ 0 is input to the single cells D9, D8 D1, DO, and the battery cells D9, D8 D1, DO are compensated and charged until the discharge of the entire lithium ion battery pack is completed. Using the above to sort each cell voltage value from high to low, will be at the end of the sorting queue

Correction page (Article 91) The lowest voltage (ie, the lowest amount of current residual charge) is the single cell that is currently required to compensate for charging.该 This method is simple, accurate and easy to implement. As shown in FIG. 4, in order to further control the temperature of the battery pack, a temperature sensor 403 is further connected to the upper computer 300, and the temperature sensor 403 is sent to the temperature of the environment where the ion battery pack is placed in the upper position machine 300, so as to realize the temperature. control.

As shown in FIG. 4, in order to facilitate the monitoring and management of the upper computer 300, a display module 404 is further disposed on the upper computer 300, so that the user can view various performance parameters of the current lithium ion battery pack at any time, such as the current residual charge amount and temperature parameters. Etc., to achieve better lithium-ion battery pack control.

The technical solutions provided by the embodiments of the present invention are described in detail above, and the principles applied to help understand the embodiments of the present invention are applied herein. At the same time, for those skilled in the art, according to the embodiments of the present invention, The scope of the present invention and the scope of the application are subject to change. In the above description, the contents of the specification are not to be construed as limiting the invention.

Correction page (Article 91)

Claims

A power lithium ion battery pack discharge equalization method, the lithium ion battery pack comprising a plurality of unit cells connected in series, wherein:

The output end of the DC conversion circuit is electrically connected in common, and the input end of the DC conversion circuit is electrically connected to the voltage output end of the lithium ion battery; during the discharge of the lithium ion battery, the lithium ion battery is monitored in real time. The remaining charge of the group:

When the ratio of the remaining charge amount of the lithium ion battery to the total capacity of the lithium ion battery pack reaches a predetermined lower limit, the following steps are sequentially performed: collecting voltage signals of each of the single cells to obtain each single battery a voltage measurement value; determining a current battery that needs to be compensated for charging according to a voltage measurement value of each of the single cells; and turning on a switching circuit electrically connected to the current battery that needs to be compensated for charging, so that the DC conversion circuit The output end is in electrical communication with the positive and negative poles of the unit battery that is currently required to compensate for charging, so that the DC conversion circuit compensates for charging of the unit battery that needs to be compensated for charging until the discharge of the lithium ion battery pack ends.

2. The power lithium ion battery discharge equalization method according to claim 1, wherein: the predetermined lower limit is selected from any value between 20% and 30%.

3. The power lithium ion battery discharge equalization method according to claim 1 or 2, wherein:

According to the voltage measurement value of each single battery, the single battery that needs to be compensated for charging is determined according to a predetermined program. Specifically, according to the voltage measurement values of all the single cells, the average value of the current voltage measurement value is determined.

Comparing and calculating the average value of the voltage measurement value of each single cell and the voltage measurement value

Correction page (Article 91) Absolute difference value, the single cell whose absolute difference is greater than a predetermined threshold is used as a candidate cell to be equalized,

Sorting the voltage measurement values of the candidate cells to be equalized from high to low, obtaining a sorting queue, sorting the voltage measurement values by a predetermined number of single cells at the end of the sorting queue, as the current charge to be compensated Body battery.

The power lithium ion battery discharge equalization method according to claim 1 or 2, characterized in that:

The predetermined number is an integer value of 10% of the total number of cells.

5. A power lithium ion battery pack discharge equalization system, the power lithium ion battery pack comprising a plurality of unit cells connected in series, wherein:

The equalization system includes: a plurality of lower position machines, a plurality of switch circuits, a host computer, and a DC to DC DC conversion circuit;

Each of the lower-level machines is electrically connected to the positive and negative poles of each of the single cells, respectively, for collecting voltage signals of the single-cell batteries, obtaining voltage measurement values of the single-cell batteries, and each single-cell battery The voltage measurement value is transmitted to the upper computer;

The upper computer includes: a battery remaining power detecting module, a compensation charging battery determining module, and a compensation charging control module, where

The compensation rechargeable battery determination module is electrically connected to each of the lower positions, and is configured to determine, according to a predetermined procedure, a current battery that needs to be compensated for charging according to a voltage measurement value of each of the single cells.

The battery remaining power detecting module is electrically connected to the busbar of the lithium ion battery pack, and is configured to determine a residual charge amount of the lithium ion battery pack according to a bus voltage and a bus current.

Correction page (Article 91) The compensation charging control module is electrically connected to the battery remaining power detecting module, the compensation charging battery determining module, each lower position machine, and each switching circuit, respectively, for when the remaining charge amount of the lithium ion battery pack accounts for the lithium ion When the ratio of the total capacity of the battery pack is less than or equal to the preset lower limit: starting each of the lower position machines, compensating the rechargeable battery determination module, and connecting a switch circuit that is currently electrically connected to compensate the charged battery cells, so that the DC conversion circuit The output end is in electrical communication with the positive and negative poles of the unit battery that is currently required to compensate for charging, so that the DC conversion circuit compensates for charging of the unit battery that needs to be compensated for charging until the discharge of the lithium ion battery pack ends.

A power lithium ion battery discharge equalization system according to claim 5, wherein: said predetermined lower limit is selected from any value between 20% and 30%.

7. The power lithium ion battery discharge equalization system according to claim 5 or 6, wherein:

The compensation charging battery determination module includes: a threshold comparison module, electrically connected to each of the lower computers, for comparing and calculating an absolute difference between an average value of a voltage measurement value of each single battery and the voltage measurement value; a sorting sub-module, which is respectively connected to the threshold comparison module and each lower-level electromechanical, for sorting the voltage values of the candidate cells to be equalized from high to low, to obtain a sorting queue, wherein the candidate to be equalized single cells are: a single cell determined in the threshold comparison module and having an absolute difference greater than a predetermined threshold; a compensated rechargeable battery determination sub-module electrically coupled to the sequencing sub-module for using a predetermined number of cells at the end of the sorting queue As the single battery that needs to be compensated for charging

8. The power lithium ion battery discharge equalization system according to claim 7, wherein: said predetermined number is: an integer value of 10% of the total number of single cells.

9. The power lithium ion battery discharge equalization system according to any one of claims 5 to 8,

Correction page (Article 91)

The claim is characterized in that: the upper computer is also electrically connected to a temperature sensor.

The power lithium ion battery discharge equalization system according to any one of claims 5 to 8, characterized in that: the display module is electrically connected to the upper computer.

11. The power lithium ion battery discharge equalization system according to any one of claims 5 to 8, wherein each of said lower computers is a programmable logic controller or a single chip microcomputer.

A power lithium ion battery discharge equalization system according to any one of claims 5 to 8, wherein each of said switching circuits is a field effect transistor.

Correction page (Article 91)